Start/stop systems are known in which the internal combustion engine is switched on and off according to a certain strategy. Start/stop systems based on the pinion starters which at the start mesh a pinion in a starter ring gear of the internal combustion engine are also known.
In start/stop systems until now, the meshing of the pinion in the ring gear and the restarting of the internal combustion engines has not been able to take place until after the complete stationary state of the driveshaft or crankshaft of the internal combustion engine. As a result, in a case of stopping, delays and adverse effects of comfort occur in certain circumstances. These delays and effects are to be avoided or shortened by the meshing of the starter or the pinion thereof in the ring gear of the internal combustion engine which is coasting to a standstill. Such a sequence is also referred to in specialist circles as a “Change of Mind”. This term indicates that a change of mind by the driver of the vehicle is associated with a new driving request with the need for a restarting or revving up of the internal combustion engine again.
Various strategies for energizing the starting motor and for meshing the starter pinion are known, for example, from DE 10 2008 040 830 A1. The strategies each assume a starting system in which the functions of “starting the starter motor” and “meshing the starter pinion” can occur independently of one another. The methods described herebelow specify various variants of the strategy for starting the starter motor and for meshing the starter pinion in the starter ring gear. The latter are associated with the objective of being able to use the advantages of the “Change of Mind” function also in the running down phase of the internal combustion engine after deactivation. Furthermore, decision criteria for carrying out a suitable strategy for the meshing of the starter in the internal combustion engine which is coasting to a standstill are specified. This is done in such a way that the primary objectives are satisfied in the best possible way for the respective application. These primary objectives include, for example, the so-called restarting period, reduction of vibrations when starting with the vehicle, reduction of noise and increasing the service life of the starting system.
Basically two aspects have to be taken into account for the selection of the meshing strategy:
On the one hand the co-ordination between the reduction in vibrations when the engine is deactivated and the improvement of the service life or reduction in noise during meshing, i.e. meshing either takes place whenever the engine comes to a standstill or meshing occurs only if a starting request (to return the internal combustion engine to the self-sustaining operating mode) is already present when the engine is coasting to a standstill.
On the other hand it is to be borne in mind that between the necessary functionality, in particular in the case of separate starting of the starter, co-ordination is carried out with the duration of the restarting when a starting request is present when the engine is coasting to a standstill. In addition, various strategies can be selected in accordance with the time of triggering of the starting request when the internal combustion engine is coasting to a standstill. It is therefore possible to select, for example, whether the meshing occurs at various rotational speeds of the internal combustion engine which are still positive or already during the swinging back. Here, the time is defined on the basis of the functionality of the starting system.